Panoramic or wide format photography captures a sequence of images that are reconstructed into a single image that takes the form of a wide strip with an elongated field of view. A panoramic image typically shows a field of view that is greater than that of a camera equipped with a wide angle lens. One way to capture a panoramic image is to mount a film camera on a tripod and take a succession of images of a scene as the camera is physically rotated. The images are subsequently “stitched” together by physically cutting and pasting together strips of exposed film where the boundaries between the edges of the film are carefully aligned.
Recently, the benefits of electronic photography have led to the general acceptance of digital cameras, that store captured images in a digital memory. Some digital cameras also provide a “panorama” feature that allows a user of the digital camera to capture a sequence of adjacent images that are subsequently digitally “stitched” together into a single image with a wide coverage of field. For example, some digital cameras with a panoramic feature can interface with a personal computer that provides software to externally join together two or more images at their edge boundaries to generate a single image with a wide panoramic format.
Two basic types of panoramic image assembly solutions for consumer-level cameras can be found in the market today. One is based on an “assist” application and the other is based on a sweep hand motion. In the assist based solution, the user is required to manually take the images after deciding, with the aid of an assistant application, that the proper overlap between images has been achieved. This flow leaves the decision of which pictures to capture for panorama image production to the user. For example, as described in commonly-assigned U.S. Patent Application Publication 2010/0033553, the existing solution for creating a panoramic image requires the user to take a few images with proper overlap (the user is guided by the camera with an assist application to take the pictures with the proper overlap) and then these images are stitched together into a panoramic image. This is a cumbersome process for the user and it might also result in failure to stitch the images for several reasons. First, the overlap between the images might not be within the required margins. Second, the scene may change while taking consecutive images; for example, lighting conditions may change, or object motion may be introduced.
Newer cameras in the market provide a feature where, for example, by pressing a button and sweeping the camera across the scene, images with proper overlap are captured automatically. Some cameras may capture images until the pressed button is released, or until a memory is full, or an overall image of predetermined size is captured, or a predetermined number of pictures are captured, or the sweep motion is ended, etc. A panoramic view is then created using the captured images. However, as shown by experimentation, this flow may produce unsatisfactory results when there is large local motion (e.g. passing cars, pedestrians, or animals) in the sequence of captured images. Some of the solutions that can be found in the market compose the panorama by stitching together narrow stripes from a large number of images from the capture sequence. A less desirable panoramic image having a stripe-like appearance sometimes results.
This patent application describes a solution to these challenges.